fault code and poor maf reading

[chopper]

im running a stage 2+ golf gti edition 30, but i keep getting this fault code
1 Fault Found:

008342 - Post-Catalyst Oxygen (Lambda) Sensor Correction; Bank 1
               P2096 - 002 - Too Lean - Intermittent - MIL ON
             Freeze Frame:
                    Fault Status: 10100010
                    Fault Priority: 2
                    Fault Frequency: 5
                    Mileage: 109874 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 07:48:42

             Freeze Frame:
                    RPM: 2142 /min
                    Load: 29.8 %
                    Speed: 86.0 km/h
                    Temperature: 81.0∞C
                    Temperature: 6.0∞C
                    Absolute Pres.: 1000.0 mbar
                    Voltage: 14.224 V


Readiness: 0000 0000

Could it be an exhaust leak?

on another note i ran some 4th gear logs today and my MAF reading is only just over 210 and dropping off to 180 in high revs. I have a forge twintake... surely it should be more than this and shouldnt be dropping off?
any suggestions ? 

[rich83]

I would have thought that MAF figures of around 260-270g/s are what you should be getting

[chopper]

those of the sort of figures (260-270) i would have expected - cant understand why the forge twintake  isnt producing the goods.

[rich83]

Maybe the filters are in the wrong way around. 

What was it doing pre-twintake? What were the figures?

[Leach76]

Ok dont want to sound stupid here incase i am missing something but why arent you looking at the part that is saying about the pre-cat lambda sensor rather than talking about the maf readings ? surely if you have a knackered oxy sensor the fuelling is not going to be correct ?